Diaphragm or separator.



C. J. THATCHER.

DIAPHRAGM 0R SEPARATOH.

APPLICATION FILED MAR. 22. 191a.

1131111It??? Patented. Jan. 14,1919.

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To all whom it may concern:

Be it known that l, CHARIJES d. THATcnEn, acitizen of the United States, and a resident .of New York city, in the county of New York and State of New York, have invented certain new and useful Improvements m Diaphragms or Separators, of whichthe following is a specification.

Th1s invent1on relates to lmprovements 1n separators or diaphragms for use in sepa rating two liquids from one another, as, for example, in an electrolytic cell.

The object of the invention is to provide diaphra'gms of ample mechanical. strength which shall also be capable of withstanding the action of corrosive electrolytes-particularly of hot, alkaline or acid liquids-but nevertheless be soconstructed as to permggt of uniform distribution of a superior ion transmitting medium, which medium shall at the same time, serve to eliminate transfusion of anolyte and "catholyte liquids into one another. I

The drawing illustrates an enlarged sec= tion of my improved diaphragm or separator and shows the substantially uniform size and distribution of the voids a, a, and the character of the grains of material 6, b, and their bonding, fused or other joints at the points of juxtaposition, c. c."

For the purposes of my invention I prefer to use plates, cylinders or other vessels, composed of substantially uniform grains of lid gether as by incipient fusion.

mineral or other materials cemented tocomposed of grains of sand or crystalline silica, and alundum, composed of granular aluminum omd, are good examples'of such materials. They are admirably suited to the purpose of my invention because they contain a high percentage of voids, which are uniform in size and uniformly distributed throughout the material. These character istics, together with their mechanical strength, make such materials admirablefon the construction of diaphragms for the most varied kinds of large electrolytic cells and vats,

' These materials of course are. unaffected by acids. They have certain ,defects, how ever, which militate a ainst their general use fordiaphragms. They are slowly disintegrated and dissolved by hot, strongly alkaline liquids and they are so'porous that the anolyte and catholyte min withconsiderable rapidity, even through the densest nuns r. rnarcnnn, or new roan, it. u.

' fipecification of Letters latent. p ta t {it an, .tgt any application filed March ac, 1915'. Serial 1*]? 0. 16,285. V I

said materials for diaphragms ll proceed as follows:

For preparing diaphragms or separators for use in electrolytic cells of any kind or in 1 similar apparatus, ll use preferably coarsely grained plates or cylinders, e39. .filt'ros or alundum having coarse, more or less uniform grains cemented together substantially only at their points of juxtaposition. Suchcoarsely grained filtros or alundum plates, etc., are more porous, and contain a larger percentage of voids. Their voids are more uniform in size and more uniformly distributed throughout the material than in the case of the finer grained materials which have hitherto been selected for diaphragms, in order to reduce, as far as possible, the undesirable transfusion therethrou h. of the. anolyte and catholyte into one anot er; The drawing, which shows a somewhat enlarged section of my improved diaphragm, illustrates the fore oing description of the class of materials w' ich l preferably employ.

ll will describe first the preparation from such materials of diaphragms intended to be used only for alkaline liquids. 1

The porous plate or vessel, preferably dry or nearly so, is first saturated with a solution of a salt of a metal which is capable of forming gelatinous hydrates, insoluble in caustic alkalis. I Magnesium is an example of such a metal, and the porous material -may' be soaked in a solution of magnesium sulfate, for example, the solution being preferably quite concentrated.

After the porous material has become well saturated with this solution, T- remove .it therefrom, and then immerse it in a solution of'a hydrate such as sodium hydronid. A ten per cent. solution sufl'ices, but more dilute or more concentrated solutions may be emp yed, The porous material should Tilt ltlli lld of the caustic soda solution by diffusion to the innermost parts of the porous material will not be rapid because all of the ,m surface interstices and pores of the material become filled immediately with a gelatinous medium, consisting of hydrate of magnesium, which cannot be washed out of the pores but effectually and permanently fills them, thereby making the porous ma terial substantially impermeable to liquids. Ions, however,'will migrate through the moist, gelatinous material as readily as through water.

After this precipitation of the gelatinous substance, the impregnated material may be immersed for some hours in water to allow the sulfates or other salts of the alkali metals to diffuse out, if that is thought necessary. The plates are'then ready for use; they will be moist because of the water retained by the gelatinous hydrate, and should be preferably maintained in a moist condition so that the gelatinous material 1 will not shrink up by drying and cease to fill the pores. In some instances, however,

later moistening of the diaphragm material and thereby of the gelatinous substance contained therein may cause the gelatinous'suibstance to swell u and again effectually close the pores of material; But to prevent such drying and shrinking of the gelatinous substance, as for example during shipment of the diaphragms, calcium chlorid, caustic soda, or other hygroscopic substances may be applied to the surfaces or introduced into the in terior of the impregnated, diaphragm material, as by immersing the latter in a solution of the specified hygroscopic substances, and with the result that the plates will permanently retain their moist condition. These hygroscopic substances, of course, if they are undesirable, can be subsequently washed out before use, but the impregnated material thereafter should be preferably maintained in a moist condition.

It will be understood that care should be taken to have all parts of the porous materialequally saturated with the magnesium sulfate solution, and then with the alkali solution, and thatthese treatments may be efiected in reverse order and also while the diaphragm material is in place in the celhin which it is .to be used. Electrolysis, using the magnesium sulfate solution as anolyte and the solution of the hydrate as catholyte, will of course facilitate precipitation of the gelatinous hydrate in the pores of the intervening diaphragm material where the -without serious disintegration.

the diaphragm" migrating magnesium and hydroxyl ions meet.

By thus precipitating hydrates, which are practically insoluble in alkalis, in the pores of materials such as filtros or alundum, they become more resistant to alkaline liquids, which effect it is one of the objects to that exerted by the metal and hydroxyl ions introduced into the plate by electrolsis. y Furthermore, in the case of silicious ma terials such as filtros, as soon as there is any solution, by the caustic alkali, of silica at any point, the resulting alkaline silicate solution immediately reacts with the adjacent magnesium hydrate forming, in situ, dense, gelatinous magnesium silicate, as a coating around the solid particle of silica which had been attacked, and thereby serves to eliminate further access to and solvent action upon the silica by the caustic liquid. Filtros or similar granular materials, when thus treated, may be used continuously for long periods in hot, alkaline liquids Such impregnated diaphrgams have an electrical resistance, which, providing they contain 50% of voids for example, is only about twice as great as a body of the electrolyte having the same dimensions as the plate. By volume the diaphragms are composed of 50%, for example, of a good conducting, gelatinous material, which is practicallly impermeable to liquids and which is uni duct the current uniformly throughout and which are practically impermeable to liquids; and which, in case magnesium hydrate is used as a gelatinous medium, are not measurably disintegrated by corrosive, alkaline liquids. V

Diaphragms made by the previously described process cannot be used in ammoniacal nor in acid solutions, both of which of course dissolve the gelatinous magnesium or other hydrate.

In constructing diaphragms for use in solutions of ammonia or its S I impreg' lid restate nate the plate with gelatinous hydrate of alumina or with the hydrate of some other metal which is insoluble in ammoniacal solutions. This is accomplished by carrying out the treatments previously described, su stituting a soluble salt of alumina for the magnesium sulfate and a solution of ammonium hydroxid for the caustic soda solution. The result will be a diaphragm composed of uniformly distributed, gelatinous aluminum hydrate, embedded in coarse grained silica or aluminum oxid and, which will not be attacked by ammoniacal solutions, and will moreover possess all the advantageous properties of the improved diaphragms heretofore described.

Diagrams which are to be used in either acid or alkaline liquids or with an acid liquid on one side of the diaphragm and an alkaline on the other, are similarly produced by impregnating filtrous, alundum or similar granular material with gelatinous magnesium silicate or equivalent gelatinous silicates which are not dissolved by acids or alkalis. It Will be readily understoodthat this can be accomplished by carrying out the treatments previously specified for the production of diaphragms impregnated with magnesium hydrate, substituting a more or less concentrated solu tion of water-glass for the caustic soda specified for use in that treatment. In this case it would be preferable to first saturate the suitable filtros or alundum material with the sodium silicate solution and then with the magnesium or other metallic salt solution. Subsequent washing and addition of hygroscopic substances may be employed, substantially as before described. Such impregnated diaphrgams will have all of the novel characteristics previously set forth and in addition thereto be capable of use for prolonged periods in either acid or alkaline liquids, or in both. As soon as solution of silica by caustic soda, for example, begins at any point, the resulting sodium silicate reacts with the magnesium silicate to form a more silicious magnesium silicate or double silicate of sodium and magnesium, and with the result that the diaphragm material does not Waste away and that further solution is substantially eliminated.

Diaphragms suitable for prolonged use in acid liquids, having a uniform and maximum permeability to migrating ions but not permeable to liquids may be similarly constructed by impregnating filti-os, alundum or similar uniformly, granular materials With gelatinous hydrate of silica, which is insoluble in acids, as are also the porous materials specified. It will be also under stood that this impregnation can be effected by immersing such materials, first in a Water-glass solution of considerable strength, and then in diluted sulfuric or other acids, which will cause a precipitation, within the voids, of gelatinous silica hydrates with the results hitherto specified. Subsequent waslr, ing out of sodium sulfate, etc., may be resorted to if that seems desirable; and by thereafter introducing or by retaining some sulfuric acid within the gelatinous medium it will be hygroscopic and the drying out of the gelatinous material which is undesirable will be avoided.

The diaphragms previously described, prepared by impregnating liltros, alundum, or other uniformly granular materials with magnesium or aluminum or other hydrates, or with magnesium silicate or silica hydrates, may of course be used with neutral liquids, proper care being taken to select a gelatinous impregnating medium which is adapted to the liquid or liquids in \vhich'it is being used. A diaphragm impregnated with magnesium hydroxid should not be used in. a neutral solution containing ammonia salts, for example, because the latter exert a solvent action upon magnesium hydrate.

I claim:

1. An electrolytically good conducting, substantially non-filtering medium suitable for diaphragms, consisting of a non-cellular, granular, structure and of a gelatinous impregnating material.

2. An electrolytically good conducting, substantially non-filtering medium suitable for diaphragms, consisting of a non-cellular, granular structure containing a high percentage of voids, and of a gelatinous medium in said voids.

3. An electrolytically good conducting, substantially non-filtering medium suitable for diaphragms, consisting of a non-cellular granular structure containing substantially uniformly distributed voids, and of a gelatinous medium in said voids.

4:. An electrolytically good conducting, substantially nonfiltering medium suitable for diaphragms, consisting of a non-cellular, granular silica structure and of a gelatinous impregnating material.

5. An electrolytically good conducting, substantially non-filtering medium suitable for diaphragms, consisting of a rigid, porous, non-cellular structure composed of cohering grains of silica, and of a gelatinous silicious impregnating material.

Signed at New York city, in the county of New York and State of New York, this 20th day of March, A. D. 1915.

CHARLES J. THATCHER.

Witnesses ARTHUR WORISCHEK, LAURA E. SMITH.

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